slack provides only two types of responses:
ok so i found my question's answer, it is said in slack's api that
The only user-facing difference between immediate responses and delayed responses is that "in channel" delayed responses will not include the initial command sent by the user. To echo the command back to the channel, you'll still need to provide a response to Slack's original visit to your invocation URL.
reference https://api.slack.com/slash-commands#responding_to_a_command